The term zener diode has long been applied to twoelectrode semiconductor devices operating with respect to the phenomena of the breakdown in solid dielectrics below approximately 5 volts, and of the avalanche effect corresponding to the townsend discharge effect in dielectrics at potentials above approximately 5 volts. Zener diode devices are widely used as potential or "voltage" regulating devices, particularly in reference potential generating circuitry. Conventional IC devices very frequently include a number of zener diode devices, a number of transistor devices, and auxiliary circuit components and connections on a single semiconductor wafer or chip.
As the electronics arts have progressed, better and better zener diode devices and circuit arrangements have been developed. Examples of such improved zener diode circuits are found in the technical literature. There have been problems however with the prior art devices, for example, especially with respect to variations of the breakdown voltage, as a function of time and/or changes in temperature. It has been suggested that the causes of instability are related to the presence of the passivating insulating layer of silicon dioxide which lies adjacent to the silicon facing surface where avalanche breakdown takes place in the conventional zener diode devices. The prior art contains literature and patents that have proposed fabricating zener diode devices with subsurface avalanche breakdown regions, and to the extent that they are able, these prior art arrangements have proven successful. However, among the drawbacks of the present state of the art subsurface zener diodes are that an n.sup.+ diffusion into a p.sup.+ base results in a p pinch resistance that tends to a high dynamic impedance. Another drawback resides in considerable deformation damage due to diffusing a high emitter n.sup.+ concentration into a high p.sup.+ concentration resulting in problems in reliability and consequent reduction in yield.